Polygeneration systems

ABSTRACT

A polygeneration system, wherein the various units of the polygeneration system are integrated to effectively separate the undesired species. In one embodiment, a polygeneration system is provided that includes a syngas generator for producing a syngas, a syngas enrichment unit for separating undesired species from the syngas to produce an enriched syngas and a syngas utilization system that utilizes the enriched syngas to produce useful products and a stream to facilitate the separation of undesired species in the syngas enrichment unit. In some embodiments, the polygeneration system includes membrane reactor, catalytic burner and power generation unit.

This invention was made with Government support under contract numberDE-FC26-05NT42451 awarded by Department of Energy. The Government hascertain rights in the invention.

BACKGROUND

The invention relates generally to a polygeneration system and morespecifically to integrating the various units of a polygeneration systemto effectively separate the undesired species.

The effect of industrialization on the environment has been a subject ofmany scientific debates and recent discussions are focused on the effectof greenhouse gases on global warming. Power generation and largechemical industries are among the contributors to the total greenhousegas emissions. These are single point sources of emissions compared tothe distributed nature of emissions from other sources such as theautomobile. Containing the greenhouse gas emissions from single pointsources such as power generation is desirable in reducing the totalgreenhouse gas emissions.

There are various technologies being developed for reducing thegreenhouse gas emissions, especially carbon dioxide from power plants aswell as chemical industries. Both pre-combustion and post-combustioncapture of carbon dioxide are the focus of intense studies in the recenttimes. In order to make power generation or chemical production anenvironmentally friendly process, it is important to separate all theundesired species, including carbon dioxide that would have otherwisebeen emitted to the environment. Separation of undesired species adds tothe total cost of producing power or chemicals, hence technologies thatenable capture of these undesired species efficiently are desired.

BRIEF DESCRIPTION

According to one aspect, a polygeneration system is provided thatincludes a syngas generator for producing a syngas, a syngas enrichmentunit for separating undesired species from the syngas to produce anenriched syngas and a syngas utilization system that utilizes theenriched syngas to produce useful products and a stream to facilitatethe separation of undesired species in the syngas enrichment unit. Insome embodiments, the polygeneration system includes a gasifier, aparticulate removal unit, a water gas shift unit and a power generationunit.

In another aspect, a polygeneration system includes a syngas generatorfor producing syngas, a syngas enrichment unit for separating undesiredspecies from the syngas to produce an enriched syngas and a powergeneration unit that includes a gas turbine system for combusting theenriched syngas and to produce a hot expanded gas. The hot expanded gasis used to produce a first portion of steam in the steam generationsystem. The power generation system includes a steam turbine system thatuses the first portion of steam from the steam generation system toproduce power and a second portion of steam. The second portion of steamis used to facilitate separation of the undesired species in the syngasenrichment unit.

In yet another aspect, a polygeneration system includes a syngasgenerator for producing syngas, a syngas enrichment unit for separatingundesired species from the syngas to produce an enriched syngas and afluid stream comprising said undesired species. The polygenerationsystem includes a power generation unit that includes a gas turbinesystem for combusting the enriched syngas and a hot expanded gas. Thehot expanded gas is used to produce a first portion of steam in thesteam generation system. The power generation system includes a rankineturbine that uses said first portion of steam and the fluid streamcomprising said undesired species from the syngas enrichment unit toproduce power and a second portion of steam. The second portion of steamis used to facilitate the separation of said undesired species in thesyngas enrichment unit.

In yet another aspect, a polygeneration system includes a syngasgenerator for producing a syngas, a syngas enrichment unit that includesa water gas shift unit and a separation unit. The water gas shift unitreceives said syngas and produces a hydrogen enriched syngas. Theundesired species are separated from the hydrogen enriched syngas toproduce an enriched syngas and a fluid stream comprising said undesiredspecies. The polygeneration system includes a power generation unitcomprising a gas turbine system, a steam generation system and a rankineturbine system. The enriched syngas is combusted in the gas turbinesystem to produce power and a hot expanded gas. The hot expanded gas isreceived by the steam generation system to produce a first portion and asecond portion of steam. The first portion of steam and the fluid streamcomprising said undesired species are received by the rankine turbinesystem to produce power and a third portion of steam. The third portionof steam is provided to the separation unit to facilitate the separationof said undesired species.

In yet another aspect, a polygeneration system comprises an airseparation unit, a syngas generator, a syngas enrichment unit, acatalytic burner and a power generation unit. An oxygen rich stream isproduced in the air separation unit, which is sent to the syngasgenerator. The syngas generator includes a gasifier that is configuredto receive a carbonaceous fuel and said oxygen rich stream to producesyngas. The syngas generator further includes a cooling unit to receivesaid syngas and to produce a cooled syngas. The syngas enrichment unitcomprises a particulate removal unit, a syngas sweetening unit, a watergas shift reactor and a separation unit. The cooled syngas is receivedby the particulate removal unit to produce a particulate free syngas,which is received by the syngas sweetening unit to produce a sweetsyngas. The water gas shift unit is configured to receive said sweetsyngas and a first portion of steam to produce an hydrogen enrichedsyngas and a first portion of steam. The separation unit is configuredto receive said hydrogen enriched syngas to produce an enriched syngasand a fluid stream comprising said undesired species. The fluid streamcomprising said undesired species is sent to the catalytic burner toproduce a non-flammable stream. The power generation unit comprises agas turbine system, a steam generation system and a rankine turbinesystem. The gas turbine is configured to receive said enriched syngas toproduce power and a hot expanded gas, which is received by the steamgeneration system to produce said first portion of steam and a secondportion of steam. The rankine turbine system receives said secondportion of steam and said non-flammable fluid stream to produce powerand a third portion of steam, which is sent to said separation unit tofacilitate separation of said undesired species.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 depicts a first embodiment of the instant invention;

FIG. 2 depicts a second embodiment of the instant invention;

FIG. 3 depicts a third embodiment of the instant invention;

FIG. 4 depicts a fourth embodiment of the instant invention;

FIG. 5 depicts a fifth embodiment of the instant invention;

FIG. 6 depicts a sixth embodiment of the instant invention;

FIG. 7 depicts a seventh embodiment of the instant invention;

FIG. 8 depicts a eighth embodiment of the instant invention;

FIG. 9 depicts a ninth embodiment of the instant invention;

FIG. 10 depicts a tenth embodiment of the instant invention;

FIG. 11 depicts a eleventh embodiment of the instant invention;

FIG. 12 depicts an exemplary membrane reactor;

FIG. 13 depicts a twelfth embodiment of the instant invention;

FIG. 14 depicts a thirteenth embodiment of the instant invention; and

FIG. 15 depicts an exemplary power generation unit.

DETAILED DESCRIPTION

A polygeneration system 10 includes a syngas generator 4, a syngasenrichment unit 8 and a syngas utilization system 18, as shown inFIG. 1. A carbonaceous fuel 2 is converted to a syngas 6 in the syngasgenerator 4, which syngas 6 typically includes hydrogen and carbonmonoxide. The syngas 6 is enriched in the syngas enrichment unit 8 toproduce an enriched syngas 14. The enriched syngas 14 is used in thesyngas utilization system 18 to produce useful products 22. A fluidstream 16 from the syngas utilization system 18 is used to facilitatethe syngas enrichment in the syngas enrichment unit 8 to produce theenriched syngas 14 from the syngas 6.

Carbonaceous fuel 2 comprises, for example, coal, oil, natural gas,biomass, waste, or any other carbonaceous material. The carbonaceousfuel 2 is converted to the syngas 6 in the syngas generator 4 by aconventional process, including, but not limiting to gasification,partial oxidation, reforming and auto-thermal reforming. In oneembodiment, the syngas generator 4 comprises a reactor unit and includesfor example, a reformer; a partial oxidation (POX) reactor; anautothermal reactor and a gasifier. In one embodiment, the syngasgenerator 4 may further comprise a provision for cooling the syngas 6.In another embodiment, unconverted carbonaceous fuel in the syngasgenerator 4 is recycled back (not shown in FIG. 1) to be mixed with thecarbonaceous fuel 2.

In the syngas enrichment unit 8, the syngas 6 is enriched to produce theenriched syngas 14. Enrichment of syngas 6 is typically achieved byincreasing the hydrogen and/or carbon monoxide concentration in thesyngas 6. The syngas 6 may include some undesired species that can beseparated from the syngas 6 in the syngas enrichment unit 8. In oneembodiment, enrichment of the syngas 6 is achieved by separating theundesired species. The undesired species includes, but is not limited toparticulates, sulfur compounds, carbon compounds, chlorine compounds,nitrogen compounds, water, mercury and ammonia. Some of the undesiredspecies originate from the carbonaceous fuel 2, while the others getgenerated in the syngas generator 4. In one embodiment, the syngasenrichment unit 8 is configured to produce a waste stream 12 containingthe undesired species. In one embodiment, separating at least a portionof the undesired species in the syngas enrichment unit 8 increases thehydrogen and/or carbon dioxide concentration in the syngas 6.

In one embodiment, the hydrogen concentration in the syngas 6 isincreased by a reaction of syngas 6 with water or steam, generally knownas a water gas shift reaction. The water gas shift reaction is aninorganic chemical reaction in which water and carbon monoxide react toform carbon dioxide and hydrogen and is represented as

CO+H₂O→CO₂+H₂

In one embodiment, removing at least a portion of the hydrogen from thesyngas 6 increases the carbon monoxide concentration. In anotherembodiment, the carbon monoxide concentration in the syngas 6 isincreased by the reaction of carbon dioxide and carbon to form carbonmonoxide, generally known as reverse boudouard reaction, which isrepresented by

CO₂+C→2CO

The syngas utilization system 18 is a unit that produces the usefulproducts 22, including for example, power and chemicals. The syngasutilization system 18 is configured to receive the enriched syngas 14and to produce the fluid stream 16. In one embodiment, the fluid stream16 facilitates syngas enrichment by providing the heat required for thesyngas enrichment. In another embodiment, the fluid stream 16 providesthe pressure required for the syngas enrichment. In yet anotherembodiment, the fluid stream 16 provides the steam requirements of thesyngas enrichment.

A polygeneration system 20 of the instant invention is shown in FIG. 2.The exemplary polygeneration system 20 includes the syngas generator 4,the syngas enrichment unit 8 and the syngas utilization system 18. Inone embodiment, the syngas utilization system 18 includes a chemicalsynthesis unit 24 producing the chemicals or a power generation unit 32producing the power or both. In one embodiment, as shown in FIG. 2, thesyngas utilization system 18 includes both the chemical synthesis unit24 and the power generation unit 32.

The chemical synthesis unit 24 is configured to receive a portion of theenriched syngas 14 from the syngas enrichment unit 8 to produce thechemicals including hydrogen, ammonia, dimethyl ether, methanol orliquid hydrocarbons. In one embodiment, the chemical synthesis unit 24employs Fischer-Tropsch process to produce hydrocarbons such as but notlimited to gasoline and diesel. The power generation unit 32 isconfigured to receive a portion of the enriched syngas 14 as a fuelsource to produce the power.

In one embodiment, the power generation unit 32 is a combined cyclepower plant. A typical combined cycle power plant includes a gas turbineplant, a heat recovery steam generator (HRSG) and a steam turbine plant.In the gas turbine plant, a fuel is combusted to produce a pressurizedcombusted gas that is expanded to produce the power and the hot expandedgas from the gas turbine is sent to the HRSG, which produceshigh-pressure steam that is expanded in a steam turbine plant togenerate additional power. Using the enriched syngas 14 as the fuelsource in the combined cycle power plant has many advantages includingclean and efficient burning of the fuel, clean exhaust to theatmosphere, and efficient capture of greenhouse gases including carbondioxide. In one embodiment, the power generation unit 32 is a simplecycle gas turbine plant using the enriched syngas 14 as a fuel source.In another embodiment, the power generation unit 32 is a steam turbineplant that uses the enriched syngas 14 in boilers either as a singlesource of fuel or combined with other fuels to produce high-pressuresteam that runs the steam turbine. Other fuels that can be used alongwith the enriched syngas 14 include but are not limited to coal,biomass, oil and natural gas.

As described in the previous embodiment, the fluid stream 16 from thesyngas utilization system 18 facilitates the enrichment of the syngas 6in the syngas enrichment unit 8. In one embodiment, the fluid stream 16is an inert gas stream from the chemical synthesis unit 24. In anotherembodiment, the fluid stream 16 is steam generated in the HRSG. In yetanother embodiment, the fluid stream 16 is the steam partially expandedin the steam turbine.

A polygeneration system 30 of the instant invention is shown in FIG. 3.In the exemplary polygeneration system 30, the power generation unit 32includes a gas turbine 34, a steam generator 36 and a steam turbine 38.The power generation unit 32 produces power 42 and a clean exhaust 44.The clean exhaust 44 has lower concentration of emissions as compared tothat from a conventional pulverized coal power plant. The emissionsinclude but are not limited to nitrogen compounds, sulfur compounds,chlorine compounds, mercury, ammonia and carbon dioxide. The gas turbine34 includes a compressor to compress an oxygen containing stream(oxidant) such as air, a combustor for combusting the fuel with thecompressed oxidant to generate the pressurized combusted gas (not shownin FIG. 3). In one embodiment, the enriched syngas 14 is used as thefuel in the combustor of the gas turbine 34. The gas turbine 34 includesan expander to expand the pressurized combusted gas, which expander iscoupled to a generator (not shown in figure) to produce the power 42 anda hot expanded gas 46. The hot expanded gas 46 from the gas turbine 34is sent to the steam generator 36 that produces a high-pressure steam 48using the heat content of the expanded gas 46. The high-pressure steam48 generated in the steam generator 36 is expanded in the steam turbine38 to produce the power 42.

In one embodiment, the gas turbine 34 and the steam turbine 38 arecoupled to the same generator. In one embodiment, the steam turbine 38is a reheat turbine wherein the steam flow is taken out from ahigh-pressure section and returned to an intermediate pressure sectionafter adding additional heat in the steam generator 36, therebyincreasing the net power output. In one embodiment, a partially expandedfluid stream 28 is taken from the steam turbine 38 to be used in thesyngas enrichment unit 8 to facilitate the separation of the undesiredspecies from the syngas 6 to produce the enriched syngas 14.

Separation of the undesired species from the syngas 6 is achieved by asuitable technique, including physical and chemical separationtechniques. In one embodiment, the particulates in the syngas 6 areseparated by washing the syngas 6 with water. In another embodiment,some of the undesired species including the sulfur compounds areseparated from the syngas 6 by scrubbing the syngas 6 with an aminesolution. In yet another embodiment, some of the undesired speciesincluding sulfur compounds and carbon compounds are separated by usingan absorption technique employing a solvent.

In one embodiment, a membrane separation technique is used to separatethe undesired species from the syngas 6. Driving forces in a membraneseparation technique include pressure, and/or concentration differenceacross the membrane. In a simple membrane separation process, feedstream is fed on one side of the membrane, wherein the membrane hasdifferent permeabilities for different species, thus effectingseparation of the species. Permeability is defined as the molar flow ofa species across the membrane per unit area of the membrane in unittime. A carrier stream is usually employed to carry the species thatpermeated through the membrane, thereby increasing the efficiency ofseparation. The characteristics of the carrier stream are such that theseparation of the permeated species from this carrier stream can be doneby a simple process. In one embodiment, the fluid stream 28 is used ascarrier to separate the undesired species from the syngas 6.

In one embodiment, the undesired species to be separated in the syngasenrichment unit 8 is carbon dioxide and to achieve this separation amembrane that has high permeability to carbon dioxide is used. Steam isa preferred carrier for carbon dioxide as separating the carbon dioxidefrom the steam can easily be carried out by a simple process ofcondensation. In one embodiment, the fluid stream 28 is used as acarrier to efficiently carry the carbon dioxide that is permeated to theother side of the membrane.

A polygeneration system 40 of the instant invention is shown in FIG. 4.In the exemplary polygeneration system 40, the power generation unit 32includes a rankine turbine 52. In one embodiment, the syngas enrichmentunit 8 is configured to produce the waste stream 12 containing a firstportion of the undesired species and a fluid stream 54 containing asecond portion of the undesired species. In one embodiment, the fluidstream 54 along with the high-pressure steam 48 is used as the workingfluid in the rankine turbine 52. Using the fluid stream 54 as theworking fluid in the rankine turbine 52 in addition to the high-pressuresteam 48 increases the power output from the rankine turbine 52. Theworking fluid of the rankine turbine 52 may include either steam, orcarbon dioxide or nitrogen or a combination thereof. In one embodiment,the rankine turbine 52 is configured to produce a fluid stream 56, whichis sent to the syngas enrichment unit 8 to facilitate the syngasenrichment.

In one embodiment, a water gas shift reaction is used for syngasenrichment in the syngas enrichment unit 8, and the fluid stream 56 isused to provide the steam required for the water gas shift reaction. Inone embodiment, a solvent is employed to separate the undesired speciesin the syngas enrichment unit 8, and the fluid stream 56 is used toprovide the heat required for solvent regeneration. In anotherembodiment, a membrane separation technique is employed in separatingthe undesired species in the syngas enrichment unit 8, and the fluidstream 56 is used as a carrier for the undesired species that arepermeated across the membrane. In one embodiment, a first portion of theundesired species is separated as the waste stream 12 in the syngasenrichment unit 8 shown by a dotted line in FIG. 4. The fluid stream 54carrying the second portion of the undesired species is expanded in therankine turbine 52 and the second portion of the undesired species isseparated as a fluid stream 13 from the power generation unit 32. In oneembodiment, the undesired species are separated from the syngasenrichment unit 8 as the waste stream 12 or from the power generationunit 32 as the fluid stream 13 or both.

A polygeneration system 50 of the instant invention is shown in FIG. 5.The exemplary polygeneration system 50 includes the chemical synthesisunit 24. In one embodiment, a first portion 53 of the enriched syngas 14is sent to the chemical synthesis unit 24. In another embodiment, asecond portion 55 of the enriched syngas 14 is sent to the gas turbine34 of the power generation unit 32. The combined production of chemicalsand power provides an opportunity to integrate these two processes toefficiently and economically produce both the power and the chemicals.

A polygeneration system 60 of the instant invention is shown in FIG. 6.The exemplary polygeneration system 60 includes an air separation unit(ASU) 62. In one embodiment, air 58 is separated in the air separationunit 62 into an oxygen rich stream 74 and an oxygen lean stream 68.Throughout this document, a fluid stream is said to be rich in a speciesif its concentration is greater than that in the stream from which it isgenerated. On the other hand, a fluid stream is said to be lean in aspecies if its concentration is less than that in the stream from whichit is generated.

In one embodiment, the oxygen rich stream 74 is sent to the syngasgenerator 4. Using the oxygen rich stream 74 instead of the air 58 togenerate the syngas 6 has the advantage of smaller volume of the syngasgenerator 4. Another advantage of using oxygen rich stream is theincrease in the calorific value of the syngas generated. In anotherembodiment, a first portion 66 of the fluid stream 56 is used tofacilitate air separation in the air separation unit 62 and a secondportion 64 of the fluid stream 56 is sent to the syngas enrichment unit8 to facilitate the syngas enrichment. In one embodiment, a membraneseparation technique is employed in the air separation unit 62 and thefluid stream 66 is used as a carrier for the species that is permeatedacross the membrane. In one embodiment, the membrane is permeable tooxygen. The oxygen lean stream 68 from the ASU 62 is mixed with thefluid stream 54 coming from the syngas enrichment unit 8 to form a mixedstream 72, which mixed stream 72 is sent to the rankine turbine 52.Addition of the oxygen lean stream 68 to the fluid stream 54 to formmixed stream 72 increases the mass flow to the rankine turbine 52,thereby increasing the net power output. The mixed stream 72 and thehigh-pressure steam 48 from the steam generator 36 are used as workingfluid in the rankine turbine 52. In one embodiment, a portion of theoxygen lean stream 68 is sent to the gas turbine 34 as a cooling agentshown by a dotted line in FIG. 6 to increase the efficiency of the powergeneration. Throughout this document a dotted line indicates an optionalembodiment. In another embodiment, the compressor of the gas turbineunit 34 is used to compress the air 58 of the air separation unit 62(not shown in FIG. 6).

A polygeneration system 70 of the instant invention is shown in FIG. 7.The exemplary polygeneration system 70 includes a water gas shift (WGS)unit 76 and a separation unit 78. In one embodiment, the syngas 6 fromthe syngas generator 4 is sent to the water gas shift unit 76, whereinthe water gas shift reaction takes place to produce a hydrogen enrichedsyngas 88, rich in hydrogen. In one embodiment, the hydrogen enrichedsyngas 88 is sent to the separation unit 78, to produce a fluid stream82 carrying a portion of the undesired species. In one embodiment,pluralities of separation unit 78 are employed to separate the undesiredspecies. In one embodiment, the separation unit 78 is a membraneseparator. In one embodiment, the fluid stream 82 comprising a portionof the undesired species from the separation unit 78 is sent to therankine turbine 52 as a working fluid. The fluid stream 56 is drawn fromthe rankine turbine at appropriate pressure and temperature conditionsto maximize the overall efficiency of the polygeneration system. In oneembodiment, the fluid stream 56 is drawn at the operating pressure andtemperature of the water gas shift unit 76. In another embodiment, thefluid stream 56 is drawn from the rankine turbine 52 at the operatingconditions of the separation unit 78. In yet another embodiment, thefluid stream 82 is lean in hydrogen and contains a portion of the fluidstream 56.

The WGS unit 76 can be a catalytic or non-catalytic reactor unit. Somecatalysts used in the WGS unit 76 include but not limited to the oxidesof iron, chromium, copper, zinc, cobalt, and molybdenum. The WGS unit 76can use either a sour syngas comprising sulfur compounds or a sweetsyngas devoid of sulfur compounds. Devoid is to be understood as lowconcentration of a species rather than the absence of that species. Thewater gas shift reaction is an exothermic reaction and hence generatesheat. In one embodiment, the heat generated in the water gas shiftreaction is removed from the WGS unit 76.

A polygeneration system 80 of the instant invention is shown in FIG. 8.The high-pressure steam 48 is split into two streams, a first portion 92and a second portion 94. In one embodiment, the high-pressure fluidstream 92 provides the steam required for the water gas shift reactionin the WGS unit 76, thereby enabling the operation of the WGS unit 76 athigh pressure. Operating the WGS unit 76 at high pressure isadvantageous, as it requires smaller volume of the water gas shift unit76. In one embodiment when the syngas generator 4 is operated at highpressure, operating the WGS unit 76 at high pressure improves theoverall system efficiency. In another embodiment, the rankine turbine 52is configured to receive the fluid stream 94 at high pressure, whichfluid stream 94 is partially expanded to produce the fluid stream 56 ata lower pressure than the fluid stream 94. In one embodiment, the fluidstream 56 drawn from the rankine turbine 52 is sent to the separationunit 78 to facilitate the production of the enriched syngas 14 from thehydrogen enriched syngas 88. Using the high-pressure stream 94 for thewater gas shift reaction in WGS unit 76 and the low-pressure stream 56for the separation unit is especially advantageous when a pressuredriven membrane separation process is employed.

A polygeneration system 90 of the instant invention is shown in FIG. 9.The exemplary polygeneration system 90 includes a catalytic burner 96that is configured to receive the fluid stream 82 from the separationunit 78. In one embodiment, the fluid stream 82 from the separation unit78 comprises hydrogen or carbon monoxide that is burned in the catalyticburner 96. When a membrane separation technique is used in theseparation unit 78, some amount of hydrogen and carbon monoxide permeateacross the membrane along with the undesired species that are separatedin the separation unit 78 and thus become part of the fluid stream 82,which is sent to the rankine turbine 52 as a working fluid. It isdesirable to limit the concentration of hydrogen and/or carbon monoxidein the fluid stream that is used as a working fluid in the rankineturbine 52 for at least two reasons. One is the loss of the calorificvalue of these species when they are separated from the power generationunit 32 and another is the safety hazard that hydrogen and carbonmonoxide could pose owing to their flammable nature if let into theatmosphere in the power generation unit 32. Thus, using the catalyticburner 96 that is capable of operating at very low concentration ofhydrogen and/or carbon dioxide is advantageous. In one embodiment, thecatalytic burner 96 is configured to receive the fluid stream 82carrying a portion of the undesired species and to produce heat and anon-flammable fluid stream 98.

A polygeneration system 100 of the instant invention is shown in FIG.10. In one embodiment of the exemplary polygeneration system 100, thefluid stream 56 from the rankine turbine 52 is split into two streams, afirst portion 102 and a second portion 104. In one embodiment, the fluidstream 102 is sent to the steam generator 36 and the fluid stream 104 issent to the separation unit 78 of the syngas enrichment unit 8. Oneadvantage of sending the fluid stream 102 to steam generator 36 is toincrease the heat content, which in turn increases the overallefficiency of the polygeneration system 100.

A polygeneration system 110 of the instant invention is shown in FIG.11. The exemplary polygeneration system 110 includes the syngasenrichment unit 8 comprising an impurity removal unit 106 and a membranereactor 118. The impurity removal unit 106 separates a portion of theundesired species from the syngas 6 and produces a purified syngas 122.In one embodiment, the water gas shift unit 76 and the separation unit78 are combined into the membrane reactor 118. The membrane reactor 118is configured to receive the purified syngas 122 and to produce theenriched syngas 14 and the fluid stream 82 carrying a portion of theundesired species. In one embodiment, the fluid stream 56 drawn from therankine turbine 52 is split into three streams, the first fluid stream102 that is sent to the steam generator 36, the second fluid stream 104that is sent to the separation unit 78 of the membrane reactor 118 and athird fluid stream 114 that is sent to the impurity removal unit 106.

In one embodiment, the impurity removal unit 106 substantially removessome of the undesired species as part of a fluid stream 15, including,but is not limited to, particulates, oxides of sulfur, chlorinecompounds and ammonia. Substantial removal of the undesired species isremoving about 80% to about 95% of the total impurities. Usually themembrane reactor 118 has limited capability to handle certain types ofthe undesired species such as particulates and hence it is necessary toremove these undesired species before the syngas 6 is sent to themembrane reactor 118.

The membrane reactor 118 has a suitable configuration including forexample, hollow fiber module, spiral wound module, plate and frame typemembrane modules. In one exemplary configuration shown in FIG. 12, themembrane reactor 118 is a hollow fiber membrane module. In the membranereactor 118 the water gas shift reaction and the separation of theundesired species takes place simultaneously, thereby altering the watergas shift reaction equilibrium enhancing conversion. The enhancedconversion allows smaller reactor volumes of the water gas shift unit76, thereby helping in improving the overall system efficiency. In oneembodiment, the water gas shift catalyst is in the shell side as shownin FIG. 12. The flow of streams on either side of the membrane can be inthe same direction (co-current flow) or in opposite direction(counter-current flow). In one embodiment, the flow of streams on shelland tube side of the membrane reactor 118 is counter-current as shown inFIG. 12. In another embodiment, the flow is co-current (not shown inFIG. 12).

Referring to the exemplary polygeneration system 110 shown in FIG. 11and the membrane reactor 118 shown in FIG. 12, in one embodiment thepurified syngas 122 from the impurity removal unit 106 and the fluidstream 92 from the steam generator 36 are sent on the shell side of themembrane reactor 118, wherein the water gas shift reaction takes placeproducing carbon dioxide and hydrogen. In one embodiment, the water gasshift catalyst is placed on the shell side. In another embodiment, thereis a provision to take out the heat generated by the water gas shiftreaction (not shown in FIG. 9).

In one embodiment, the membrane is permeable to carbon dioxide and thefluid stream 104 is used as the carrier for the carbon dioxide that ispermeated across the membrane wall of the membrane reactor 118. By usinga membrane that is selectively permeable to the carbon dioxide,simultaneous separation of the carbon dioxide and increasing theconversion of the purified syngas 122 to produce hydrogen is achieved.Another advantage of employing the membrane reactor 118 is that thewater gas shift reaction can be conducted at high pressure, whichimproves the overall system efficiency when the purified syngas 122 isavailable at high pressure. The driving force for separation in themembrane reactor 118 is the pressure difference across the membrane andusing the high-pressure steam 92 as a reactant and the low-pressure flowstream 104 as the carrier for the carbon dioxide provides this drivingforce.

The fluid stream 82 carrying the components, including, but not limitedto carbon dioxide, hydrogen, carbon monoxide that are permeated acrossthe membrane is sent to the catalytic burner 96 to produce thenon-flammable fluid stream 98 that is sent to the rankine turbine 52 asa working fluid along with the high pressure steam 94. The undesirablespecies carried by the fluid stream 98 are separated as fluid stream 13after the fluid stream 98 is expanded in the rankine turbine 52. Thusintegrating the power generation unit 32 with the syngas enrichment unit8 improves the overall efficiency of the polygeneration system of thisinvention.

In another embodiment the fluid stream 114 is used to facilitate theremoval of the undesired species from the impurity removal unit 106 toproduce a fluid stream 15 carrying a portion of the undesirable species.As described in the previous embodiment, the undesired species isseparated either in the syngas enrichment unit 8 or in the powergeneration unit 32 or both.

A polygeneration system 130 of the instant invention is shown in FIG.13. The exemplary polygeneration system 130 includes a pressure swingadsorption unit (PSA) 126 to produce high purity hydrogen. The purity ofhydrogen from a PSA unit 126 is above about 95%. In one embodiment, afirst portion 124 of the enriched syngas 14 from the syngas enrichmentunit 8 is sent to the PSA unit 126 to produce high purity hydrogen(shown as H₂ in FIG. 13) and a PSA offgas stream 128, containing somehydrogen. In one embodiment, the PSA offgas stream 128 is sent to thecatalytic burner 96 to be burned along with the fluid stream 82 togenerate additional heat and to produce the non-flammable fluid stream98. A second portion 132 of the enriched syngas 14 is sent to the gasturbine unit 34 of the power generation unit 32.

A polygeneration system 140 of the instant invention is shown in FIG.14. The exemplary polygeneration system 140 includes the syngasgenerator 4 comprising a gasifier 134 and a syngas cooler 136, thesyngas enrichment unit 8 comprising a particulate removal unit 146 and asyngas sweetening unit 138. In one embodiment, the oxygen rich stream 74from the air separation unit 62 and the carbonaceous fuel 2 are fed tothe gasifier 134 to produce the syngas 6, which is cooled in the syngascooler 136 to produce a cool syngas 142. In one embodiment, the oxygenlean stream 68 from the air separation unit 62 is sent to the gasturbine 34 (not shown in FIG. 14). In one embodiment, the gasifier 134and the syngas cooler 136 are combined into a single unit and in anotherembodiment they are separate units. In one embodiment, the syngas cooler136 is a radiant syngas cooler and in another embodiment, the syngascooler 136 is a quench unit. In one embodiment, the syngas enrichmentunit 8 includes the particulate removal unit 146, the syngas sweeteningunit 138 and the membrane reactor 118. In one embodiment, the coolsyngas 142 is fed into the particulate removal unit 146 and aparticulate free syngas 152 is produced. The particulate free syngas 152is sent to the syngas sweetening unit 138 and a sweet syngas 154 and asour stream 148 are produced. The sweet syngas 154 is further fed to themembrane reactor unit 118, wherein the sweet syngas 154 undergoes watergas shift reaction in the WGS unit 76 and the undesired species areseparated in the separation unit 78 to produce the enriched syngas 14.

An exemplary power generation unit 32 is shown in FIG. 15. In oneembodiment, the rankine turbine 52 includes a high-pressure turbine(HPT) 158, an intermediate pressure turbine (IPT) 162 and a low-pressureturbine (LPT) 164. In one exemplary embodiment, the enriched syngas 14from the syngas enrichment unit is combusted in the gas turbine 34 toproduce the power 42. The hot expanded gas 46 from the gas turbine 34 issent to the steam generator 36 to produce the high-pressure steam 48 andthe clean exhaust 44, which is let into the atmosphere from a stack 156.In one embodiment, the fluid stream 92 is sent to the membrane reactor118 to participate in the water gas shift reaction. In one embodiment,the stream 92 and the enriched syngas 14 are at a pressure of about 4.5M Pa (about 45 bar). The second portion 94 of the high-pressure steam 48is expanded in the high-pressure turbine 158. The fluid stream 104 fromthe high-pressure turbine is used as carrier in the membrane reactor 118to carry the undesired species. In one embodiment, the fluid stream 104is at a pressure of about 4 M Pa (about 40 bar). The non-flammablestream 98 is expanded in the intermediate pressure turbine 162, which isconnected to a low-pressure turbine 164. The fluid stream from thelow-pressure turbine 164 is sent to a condenser, wherein the undesiredspecies are separated as the fluid stream 13 and the remaining fluid isrecirculated (not shown in FIG. 15).

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A polygeneration system comprising: a syngas generator for producinga syngas comprising carbon monoxide and hydrogen; a syngas enrichmentunit for receiving said syngas and for separating undesired speciestherefrom to produce an enriched syngas; and a syngas utilization systemfor utilizing said enriched syngas to produce useful products and afluid stream to be provided to said syngas enrichment unit to facilitateseparation of said undesired species.
 2. The polygeneration system inaccordance with claim 1, wherein said syngas is produced from acarbonaceous fuel.
 3. The polygeneration system in accordance with claim2, wherein said carbonaceous fuel comprises coal.
 4. The polygenerationsystem in accordance with claim 1, wherein said syngas generatorcomprises a gasifier and an air separation unit.
 5. The polygenerationsystem in accordance with claim 1, wherein said syngas generatorcomprises at least one of a reformer, a partial oxidation reactor, anautothermal reactor or a combination thereof.
 6. The polygenerationsystem in accordance with claim 1 further comprises a pressure swingadsorption unit.
 7. The polygeneration system in accordance with claim1, wherein said syngas generator further comprises a syngas coolingunit.
 8. The polygeneration system in accordance with claim 1, whereinsaid syngas enrichment unit comprises a water gas shift unit.
 9. Thepolygeneration system in accordance with claim 8, wherein said water gasshift unit is a membrane reactor.
 10. The polygeneration system inaccordance with claim 1, wherein said syngas enrichment unit furthercomprises a separation unit for substantially separating said undesiredspecies.
 11. The polygeneration system in accordance with claim 1,wherein said syngas enrichment unit further comprise an impurity removalunit.
 12. The polygeneration system in accordance with claim 11, whereinsaid impurity removal unit substantially separates said undesiredspecies comprising at least one of sulfur containing compounds, nitrogencontaining compounds, chlorine containing compounds, carbon containingcompounds, particulates or combinations thereof.
 13. The polygenerationsystem in accordance with claim 1, wherein said syngas utilizationsystem further comprises a power generation unit or a chemical synthesisunit or a combination thereof.
 14. The polygeneration system inaccordance with claim 13, wherein said power generation unit comprisesat least one of gas turbine, rankine turbine, steam turbine, combustor,steam generator or combinations thereof.
 15. The polygeneration systemin accordance with claim 14, wherein said steam generator is configuredto produce a first portion of steam and a steam turbine is configured toreceive said first portion of steam and to produce a second portion ofsteam, wherein said second portion of steam is provided to saidenrichment unit to facilitate separation of said undesired species. 16.The polygeneration system in accordance with claim 14, wherein saidsyngas enrichment unit is configured to produce a fluid streamcomprising said undesired species and a rankine turbine is configured toreceive a first portion of steam and said fluid stream comprising saidundesired species to produce a second portion of steam, wherein saidsecond portion of steam is provided to said enrichment unit tofacilitate separation of said undesired species.
 17. A polygenerationsystem comprising: a syngas generator for producing a syngas comprisingcarbon monoxide and hydrogen; a syngas enrichment unit for receivingsaid syngas and for separating undesired species therefrom to produce anenriched syngas; and a power generation system comprising: a gas turbinesystem for combusting said enriched syngas to produce power and a hotexpanded gas; a steam generation system for receiving said hot expandedgas to produce a first portion of steam; and a steam turbine system forreceiving said first portion of steam to produce power and a secondportion of steam, wherein said second portion of steam is provided tosaid enrichment unit to facilitate separation of said undesired species.18. A polygeneration system comprising: a syngas generator for producinga syngas comprising carbon monoxide and hydrogen; a syngas enrichmentunit for receiving said syngas and for producing an enriched syngas anda fluid stream comprising undesired species; and a power generationsystem comprising: a gas turbine system for combusting said enrichedsyngas to produce power and a hot expanded gas; a steam generationsystem for receiving said hot expanded gas to produce a first portion ofsteam; and a rankine turbine system that receives said first portion ofsteam and said fluid stream comprising undesired species to producepower and a second portion of steam, wherein said second portion ofsteam is provided to said enrichment unit to facilitate separation ofsaid undesired species.
 19. The polygeneration system in accordance withclaim 18 further comprises a chemical synthesis unit to receive aportion of said enriched syngas.
 20. The polygeneration system inaccordance with claim 18 further comprises an air separation unit toreceive a portion of said second portion of steam and to produce saidfluid stream comprising said undesired species.
 21. A polygenerationsystem comprising: a syngas generator for producing a syngas comprisingcarbon monoxide and hydrogen; a syngas enrichment unit comprising: awater gas shift unit for receiving said syngas and for producing anhydrogen enriched syngas; and a separation unit for receiving saidhydrogen enriched syngas and for separating undesired species therefromto produce an enriched syngas and a fluid stream comprising saidundesired species; a power generation system comprising: a gas turbinesystem for combusting said enriched syngas to produce power and a hotexpanded gas; a steam generation system for receiving said hot expandedgas to produce a first portion of steam; and a rankine turbine systemthat receives said first portion of steam and said fluid streamcomprising said undesired species to produce power and a second portionof steam, wherein said second portion of steam is provided to saidenrichment unit to facilitate separation of said undesired species. 22.The polygeneration system in accordance with claim 21, further comprisesa catalytic burner that receives said fluid stream comprising saidundesired species.
 23. The polygeneration system in accordance withclaim 21 further comprises a pressure swing adsorption unit configuredto receive said syngas and to produce an offgas stream to be received bysaid catalytic burner.
 24. A polygeneration system comprising: a syngasgenerator for producing a syngas comprising carbon monoxide andhydrogen; a syngas enrichment unit comprising: a water gas shift unitfor receiving said syngas and a first portion of steam to produce anhydrogen enriched syngas; and a separation unit for receiving saidhydrogen enriched syngas and for separating undesired species therefromto produce an enriched syngas and a fluid stream comprising saidundesired species; and a power generation system comprising: a gasturbine system for combusting said enriched syngas to produce power anda hot expanded gas; a steam generation system for receiving said hotexpanded gas to produce said first portion of steam and a second portionof steam; and a rankine turbine system that receives said second portionof steam and said fluid stream comprising said undesired species toproduce power and a third portion of steam, wherein said third portionof steam is provided to said separation unit to facilitate separation ofsaid undesired species
 25. A polygeneration system in accordance withclaim 24 further comprises a chemical synthesis unit that receives apart of said enriched syngas.
 26. A polygeneration system in accordancewith claim 24, wherein said syngas enrichment unit further comprise acatalytic burner to receive said fluid stream comprising said undesiredspecies.
 27. A polygeneration system comprising: an air separation unitfor receiving air and producing an oxygen rich stream; a syngasgenerator comprising: a gasifier for receiving a carbonaceous fuel andsaid oxygen rich stream to produce syngas comprising carbon monoxide andhydrogen; and a cooling unit for receiving said syngas and producing acooled syngas; a syngas enrichment unit comprising: a particulateremoval unit for receiving said cooled syngas and to produce aparticulate free syngas; a syngas sweetening unit for receiving saidparticulate free syngas and to produce a sweet syngas; a water gas shiftreactor for receiving said sweet syngas and a first portion of steam toproduce an hydrogen enriched syngas; and a separation unit for receivingsaid hydrogen enriched syngas and for separating said undesired speciestherefrom to produce an enriched syngas and a fluid stream comprisingsaid undesired species; a catalytic burner for receiving said fluidstream comprising said undesired species and to produce a non-flammablefluid stream; and a power generation system comprising: a gas turbinesystem for combusting said enriched syngas to produce power and a hotexpanded gas; a steam generation system for receiving said hot expandedgas to produce said first portion of steam and a second portion ofsteam; and a rankine turbine system that receives said second portion ofsteam and said non-flammable fluid stream to produce power and a thirdportion of steam, wherein said third portion of steam is provided tosaid separation unit to facilitate the separation of said undesiredspecies.
 28. The polygeneration system in accordance with claim 27,wherein said water gas shift reactor and said separation unit arecombined into a membrane reactor.